Chemical mechanical polishing (CMP) is used in semiconductor manufacturing processes for planarizing a wafer or other work piece. To maintain the stability and throughput of CMP, the polishing pads used in CMP should be dressed by a diamond dresser.
The function of the diamond dresser is to maintain or restore the polishing characteristics of the polishing pad to the maximum extent possible during the polishing process and in doing so, extend the useful life of the polishing pad. The dressing step may be performed simultaneously with the polishing of the wafer, or as a separate step after every wafer or an x number of wafers is polished. The diamond dresser performs this function by exerting pressure on the polishing pad thereby affecting the polishing characteristics of the polishing pad.
Diamond dressers are generally made with diamonds. The usage of diamonds and the designs of most diamond dressers are such that the last 2 mm to 3 mm towards the outer circumference of the dressers are not covered by diamonds. Therefore, when the polishing pad is dressed down, the travel of this 2 mm to 3 mm of flat outer circumference region would be obstructed by the undressed part of the pad material. Such undressed part of the polishing pad affect CMP removal rate stability and increases wafer range issues as the polishing pad ages, thus limiting any future pad consumable life extension.
From the foregoing, it is desirable to provide an improved polishing pad that addresses the issue caused by the undressed part of the pad material.